Documents the reason why it's needed and also prevents the
ensureNewerSourcesHook call being evaluated again and again for every
single Python package.
When a Python script has the extension `.py`, bytecode is generated.
Typically, executables in bin have no extension, so no bytecode is
generated. However, some packages do provide executables with
extensions, and thus bytecode is generated.
Python libraries or modules now have an attribute `pythonModule = interpreter;` to indicate
they provide Python modules for the specified `interpreter`.
The package set provides the following helper functions:
- hasPythonModule: Check whether a derivation provides a Python module.
- requiredPythonModules: Recurse into a list of Python modules, returning all Python modules that are required.
- makePythonPath: Create a PYTHONPATH from a list of Python modules.
Also included in this commit is:
- disabledIf: Helper function for disabling non-buildPythonPackage functions.
While we tell pip not to fetch (with the `--no-index` option),
`setuptools` can do so itself. In the past we used a `distutils.cfg`
with `allow-hosts = None` to prevent setuptools from fetching itself.
This was removed when we started building wheels in
2562f94de4e4fd2ddc677187fa2e2848L69.
The `dist-utils.cfg` code was still there, and adding it to
`buildInputs` is sufficient.
Tested with python.pkgs.passlib by removing the `checkInputs` / `nose`.
When tests are disabled, we do not want to pass checkInputs to
stdenv.mkDerivation. This reduces the build requirements and, more
importantly, helps cutting cycles.
The Python interpreters are patched so they can build .pyc bytecode free
of certain indeterminism.
When building Python packages we currently set
```
compiling python files.
in nix store.
DETERMINISTIC_BUILD=1;
PYTHONHASHSEED = 0;
```
Instead if setting these environment variables in the function that
builds the package, this commit sets the variables instead in the Python
setup hook. That way, whenever Python is included in a derivation, these
variables are set.
See also the issue https://github.com/NixOS/nixpkgs/issues/25707.
Python does add the script's directory into "sys.path". For the case of
"catch_conflicts.py" this means "/nix/store" is added to "sys.path". This can
result in very long delays if the store contains a lot of entries.
(moved from master commit 76213d102c)
